Development of Hard-Tissue Substitute by Superplastic Deformation of Carbonate Apatite

近年来，磷酸钙作为生物材料得到了广泛的应用。我们之前报道过烧结碳酸盐磷灰石比羟基磷灰石和β-TCP具有更高的生物相容性，可以广泛应用于骨填充和替代材料等生物材料。碳酸盐磷灰石陶瓷在高温下也表现出明显的塑性变形。为了利用碳酸盐磷灰石的高塑性变形能力，将其作为具有任意形状的硬组织替代材料，本研究进行了塑性变形（超塑性变形）发展条件和变形量的基本评估。烧结碳酸盐磷灰石被放置在一个电炉连接到Survopulser（岛津公司）。通过一个0.2 Kn的氧化铝夹具施加压力，直到试样被加热到指定的温度。此后，压力增加到10 Mpa作为初始载荷。对碳酸盐磷灰石试样进行了2h的线性尺寸测量，并对其塑性变形行为进行了研究。变形后对试样进行SEM和x射线衍射分析，评价其物理性能的变化。结果表明，当初始载荷为10 Mpa时，在700℃时发生了轻微的塑性变形。随着保温温度的升高，塑性变形量呈线性增加，在800℃时达到80%左右。通过扫描电镜观察，变形后的试样由较大的晶粒组成。加载前试样存在较大的孔隙率，加载后孔隙率减小。x射线衍射分析表明，变形后的结晶度有所改善，晶体有轻微的取向。这些结果表明变形后的物理性能有所改善。因此，烧结碳酸盐磷灰石在较低温度下具有超塑性。因此，如果对超塑性变形性能进行适当的负荷、温度和时间评价，烧结后各种形状的碳酸盐磷灰石可较少用作硬组织替代材料

In recent years, calcium phosphates have been used as biomaterials. We previously reported that sintered carbonate apatite has higher biocompatibility than hydroxyapatite and β-TCP, and can be widely applicable as biomaterials such as bone filling and replacement materials. Carbonate apatite ceramics also shows marked plastic deformation at high temperatures. To use carbonate apatite as hard tissue substitution materials with arbitary shapes utilizing this high plastic deformability, basic evaluation of the conditions for the development of plastic deformation (superplastic deformation) and the amount of deformation was performed in this study. Sintered carbonate apatites were placed in an electric furnace attached to a Survopulser (Shimazu Co.). Pressure was applied via an alumina fixture at 0.2 Kn until the specimen was heated to a designated temperature. Thereafter the preasure was increased to 10 Mpa as an initial load. The linear dimension of the carbonate apatite specimen was mea … More sured for 2hr, and the behavior of plastic deformation was examined. After the deformation, SEM and X-ray diffraction analysis of samples were performed, and changes in their physical properties were evaluated. As a result, when the initial load was 10 Mpa, slight plastic deformation occurred at 700℃. The amount of plastic deformation linearly increased with an increased in holding temperature, reaching about 80% at 800℃. When viewed with SEM, the specimens appeared to be composed of larger grains after the deformation. Considerable porosity were present in specimen before the load application, but the porosity decreased after the load application. X-ray diffraction analysis revealed the improvement in crystallinity after the deformation and a slight degree of crystal orientations. These results suggested improvement in physical properties after the deformation. Thus, sintered carbonate apatite has superplasticity at a comparatively low temperature. Thesefore, if appropriate load, temperature, and time are evaluated for the superplastic deformability, sintered carbonate apatite with various shape can be used as hard tissue substitution materials Less